// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_STRIDE_H
#define EIGEN_STRIDE_H

namespace Eigen {

/** \class Stride
 * \ingroup Core_Module
 *
 * \brief Holds strides information for Map
 *
 * This class holds the strides information for mapping arrays with strides with class Map.
 *
 * It holds two values: the inner stride and the outer stride.
 *
 * The inner stride is the pointer increment between two consecutive entries within a given row of a
 * row-major matrix or within a given column of a column-major matrix.
 *
 * The outer stride is the pointer increment between two consecutive rows of a row-major matrix or
 * between two consecutive columns of a column-major matrix.
 *
 * These two values can be passed either at compile-time as template parameters, or at runtime as
 * arguments to the constructor.
 *
 * Indeed, this class takes two template parameters:
 *  \tparam _OuterStrideAtCompileTime the outer stride, or Dynamic if you want to specify it at runtime.
 *  \tparam _InnerStrideAtCompileTime the inner stride, or Dynamic if you want to specify it at runtime.
 *
 * Here is an example:
 * \include Map_general_stride.cpp
 * Output: \verbinclude Map_general_stride.out
 *
 * Both strides can be negative, however, a negative stride of -1 cannot be specified at compiletime
 * because of the ambiguity with Dynamic which is defined to -1 (historically, negative strides were
 * not allowed).
 *
 * \sa class InnerStride, class OuterStride, \ref TopicStorageOrders
 */
template<int _OuterStrideAtCompileTime, int _InnerStrideAtCompileTime>
class Stride
{
  public:
	typedef Eigen::Index Index; ///< \deprecated since Eigen 3.3
	enum
	{
		InnerStrideAtCompileTime = _InnerStrideAtCompileTime,
		OuterStrideAtCompileTime = _OuterStrideAtCompileTime
	};

	/** Default constructor, for use when strides are fixed at compile time */
	EIGEN_DEVICE_FUNC
	Stride()
		: m_outer(OuterStrideAtCompileTime)
		, m_inner(InnerStrideAtCompileTime)
	{
		// FIXME: for Eigen 4 we should use DynamicIndex instead of Dynamic.
		// FIXME: for Eigen 4 we should also unify this API with fix<>
		eigen_assert(InnerStrideAtCompileTime != Dynamic && OuterStrideAtCompileTime != Dynamic);
	}

	/** Constructor allowing to pass the strides at runtime */
	EIGEN_DEVICE_FUNC
	Stride(Index outerStride, Index innerStride)
		: m_outer(outerStride)
		, m_inner(innerStride)
	{
	}

	/** Copy constructor */
	EIGEN_DEVICE_FUNC
	Stride(const Stride& other)
		: m_outer(other.outer())
		, m_inner(other.inner())
	{
	}

	/** \returns the outer stride */
	EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index outer() const { return m_outer.value(); }
	/** \returns the inner stride */
	EIGEN_DEVICE_FUNC EIGEN_CONSTEXPR inline Index inner() const { return m_inner.value(); }

  protected:
	internal::variable_if_dynamic<Index, OuterStrideAtCompileTime> m_outer;
	internal::variable_if_dynamic<Index, InnerStrideAtCompileTime> m_inner;
};

/** \brief Convenience specialization of Stride to specify only an inner stride
 * See class Map for some examples */
template<int Value>
class InnerStride : public Stride<0, Value>
{
	typedef Stride<0, Value> Base;

  public:
	EIGEN_DEVICE_FUNC InnerStride()
		: Base()
	{
	}
	EIGEN_DEVICE_FUNC InnerStride(Index v)
		: Base(0, v)
	{
	} // FIXME making this explicit could break valid code
};

/** \brief Convenience specialization of Stride to specify only an outer stride
 * See class Map for some examples */
template<int Value>
class OuterStride : public Stride<Value, 0>
{
	typedef Stride<Value, 0> Base;

  public:
	EIGEN_DEVICE_FUNC OuterStride()
		: Base()
	{
	}
	EIGEN_DEVICE_FUNC OuterStride(Index v)
		: Base(v, 0)
	{
	} // FIXME making this explicit could break valid code
};

} // end namespace Eigen

#endif // EIGEN_STRIDE_H
